**9. Green fertilization**

**Authors Nutrient (g kg−1)**

186 Sugarcane - Technology and Research

**Authors Nutrient (mg kg−1)**

Concentration ranges for plant cane. \*\*Concentration ranges for regrowth.

[17]

\*

**N P K Ca Mg S**

The chemical analysis of sugarcane leaves is another way for evaluating the nutritional status of crops. The preference for leaves is because, in general, they reflect better the variations in the supply of nutrients both by the soil and by fertilizations. In sugarcane, it has been recommended to collect the +2 or +3 leaves. The leaf +1 is, in the descending direction of the stem, the first leaf to show a fully visible ligule (region of insertion of the leaf sheath on the stem). For the chemical analysis, the median third of the +2 or +3 leaf is used excluding the central vein. Samples from the middle third should first be washed in clean running water and then in distilled water. Then, the material should be dried at 65°C until constant weight. If this

of these nutrients in the +3 leaf limbus, used to evaluate nutritional status, was lower than 5.0 and 40.0 mg/kg of dry matter, respectively, for copper and manganese, characterizing a severe deficiency of these elements. The high adsorption of copper and manganese sulfates may have been the cause of the absence of responses. Ref. [25] studied the adsorption of copper originat-

humic soils. They found a very high adsorption (99.4%) of copper 2 h after its addition to the soil. On the other hand, copper in the ethylene diaminotetraacetic acid and diaminocyclohexane tetraacetic acid forms presented a soil percentage adsorption of 7.3 and 5.3, respectively. Therefore, it is necessary to evaluate the efficiency of other sources of copper and manganese because the adsorption of copper and manganese sulfates by the soil was very high. In addition to compromising the productive potential of these varieties, copper and manganese deficiency leads to metabolic changes that compromise the quality of the broth. These nutrients are constituents of the polyphenol oxidase and amylase metalloenzymes [17, 26, 27]. Therefore, with a poor performance of these enzymes, there is accumulation of phenolic and starch compounds.

to sandy and

ing from several compounds. These authors studied the application of CuSO4

**8. Evaluation of the nutritional status of sugarcane**

**B Cu Fe Mn Mo Zn**

\* 15–50 8–10 200–500 100–250 0.15–0.30 25–50 [17]\*\* — 8–10 80–150 50–125 — 25–30 [28] 10–30 6–15 40–250 25–250 0.05–0.20 10–50 [29] 6–29 9–17 76–392 73–249 — —

**Table 11.** Nutrient concentration ranges in the middle third of the +2 or +3 leaf considered adequate.

[17]\* 19–21 2.0–2.4 11–13 8.0–10 2.0–3.0 2.5–3.0 [17]\*\* 20–22 1.8–2.0 13–15 5.0–7.0 2.0–2.5 2.5–3.0 [28] 18–25 1.5–3.0 10–16 2.0–8.0 1.0–3.0 1.5–3.0 [29] 16–25 2.0–3.5 6–14 4.3–7.6 1.1–3.6 1.3–2.8 Green fertilization is the cultivation of plants for the purpose of incorporating them into the soil. Among the desirable characteristics of a plant to be used as green manure, we may mention the possibility of mechanization from sowing to seed harvesting, absence of dormant seeds, vigorous and deep root system, ability to associate with nitrogen fixing bacteria in atmospheric air, fast growth to control weeds, and presence of mechanisms or synthesizing compounds that aid in the control of pests, such as nematodes, and diseases.

Several legumes have these characteristics, but generally there is a preference for *Crotalaria juncea* in the Center-South region of Brazil and for *Crotalaria spectabilis* in the states of Alagoas and Pernambuco, northeastern Brazil. *Crotalaria juncea* is a legume with a very fast initial growth, which provides it with a great competition potential with weeds. However, it is very sensitive to nictoperiods, early blooming in growing nights and, consequently, interrupting growth. Therefore, when cultivating for green manure, sowing should be performed in early October, or as soon as possible. However, for seed production, it should be sown in March.

In studies conducted by [1] in two regions of Minas Gerais, Alto Paranaíba and Zona da Mata, there was accumulation of dry matter (DM) by *Crotalaria juncea* sown in October, around 15 tons per hectare, with nitrogen concentration oscillating around 20 g of N per kg of DM. Thus, for a DM yield of 15 t ha−1, the amount of N fixed and/or recycled is 300 kg per hectare. In areas densely infested with *Brachiaria plantaginea*, the inclusion of *Crotalaria* in the system increased the mass of N over the soil by 320% since the accumulation by the natural vegetation of the fallow area was 66 kg of N per ha, while in the area with *Crotalaria*, this accumulation exceeded 250 kg ha−1, a sufficient quantity to ensure a production of 230 t of natural matter of sugarcane per hectare. Ref. [1] reported that in experiments conducted in areas where *Crotalaria* was incorporated into the soil, there was an increased productivity in plant cane of 15 t of culms per hectare compared to fallow areas.

The dry matter production of *Crotalaria juncea* and *spectabilis* in the states of Alagoas and Pernambuco oscillated around 4.5 t of DM per ha. This low production of DM, compared to that observed in the Center-South region, is mainly because the sowing season occurred at the beginning of the rainy season, between April and early May, therefore in longer nights. In Alagoas, in areas where *Crotalaria spectabilis* is used as green manure, it has been common to perform direct grooving without previous soil plowing, similar to the minimum cultivation systems adopted for some other crops.
